At Linquenda House, Harare's gloomy immigration department, the official inspecting my visa extension form asks me what I do. "I'm a wineseller," I lie. "You're not a news seller?" he shoots back, his eyes watching me mischievously. "What's that?" I say, trying to be innocent, but taken aback by his apparent mind-reading. "A journalist," he answers. "Oh, no, I'm not one of them" I say, trying to laugh. He chuckles and explains that "some of your fellow countrymen are attempting to come in and make trouble," before stamping my passport.

That was in 2002, but on subsequent trips I have been a birdwatcher, architect and cricket fan. Such is life for the "tourist" in Zimbabwe, where lying to strangers and suspicion of others becomes second nature. You know that you could be jailed for up to two years, but you are also aware that unaccredited journalists caught by the authorities are usually deported. But now, the trial of two Sunday Telegraph "tourists" arrested at a polling station during last month's parliamentary election has changed all that.

It is true that Toby Harnden and Julian Simmonds were acquitted of working without accreditation and are now safe in the UK. But without a judge who insisted on proper standards of evidence - by no means certain in Zimbabwe - they could have been spending the next two years in a crowded, disease-ridden jail cell.

Since Zimbabwe's new media laws came in three years ago, the state has sought to stop journalists from the BBC, and other news organisations it terms "agents of imperialism", from entering the country. The British media's answer has been to send in the "tourists" - an army of men and women keen to see the elephants, visit Victoria Falls and, of course, write about Mugabe. It is a peculiar existence, and one that looks increasingly dangerous.

I have spent three periods working in Zimbabwe without accreditation. Each time you arrive you promise yourself that you will keep risks to a minimum. There are the obvious steps. Keeping a pile of tourist guides, birdwatching books and half written postcards about your person, not talking to strangers about politics, not taking notes in public, ensuring your emails are not being read over your shoulder, keeping phonecalls short and discreet, and listening to the advice of locals you trust.

But despite one's good intentions, journalistic instincts are hard to suppress. Casual questions become more focused, feigned ignorance disappears, your eyes light up and before you know it, your notebook is out and you are scribbling away. The bottom line is, if you are going to do the job properly you cannot avoid taking risks. When deciding whether to interview people you constantly have to ask yourself: "Do I trust this person?" Not in the traditional sense, but on whether they will turn you in. It comes down to calculated risks.

A year after the murder of white farmer Terry Ford, I visited his farm to see what had happened to it and the "war veterans" who had taken over there. Local farmers warned me the killers were still there and did not welcome visitors. My heart thumped as I introduced myself as an aid worker and showed them a business card belonging to someone I had recently interviewed. But the risk paid off - their desperation meant they wanted to believe me. They were hungry, the farmhouse was an empty shell. I took notes and photos but did not hang around when one of them tried to ring their "boss" for me to interview. At the junction of the dirt track back to the main road I came across a couple of police Land Rovers, apparently waiting for me. My blood ran cold. "This is it," I thought, as I saw the box-shaped vehicles parked at the side of the road. But they ignored me, I turned onto the Harare road, and slowly my adrenaline levels returned to normal.

There are many such moments in Zimbabwe for the "tourist" hack. In the township of Kuwadzana during the 2002 election I was followed by plain-clothes police. The most malevolent-looking officer bade me farewell, succinctly: "If I see your face again I will shoot you." It was probably just a threat, but in a place like Kuwadzana, you do not hang around to find out.

You can never totally relax and constantly worry about being followed or whether your phone is tapped. Ultimately you rely on the goodwill of most Zimbabweans and the incompetence of Mugabe's police state.

So why do we do it? If journalists take the famous William Randolph Hearst maxim as their creed - "News is what someone does not want you to print, the rest is just advertising" - then Zimbabwe is the apotheosis of news. But after the Sunday Telegraph's close shave, it might be only freelances who are willing to take the risk.